If you have a website — which is nearly everyone and their grandmother — and have not implemented a newsletter or mailing list sign-up form, then you are totally missing out on a good monetization opportunity.
And if you carelessly shrug your shoulders at the thought of possibly monetizing your website, then at least think about the opportunity of growing organic traffic.
Executing a sound popup form upon scroll, entry, or exit, or a sidebar, footer, or header sign-up form is a MUST for every website I develop. Why?